The present invention relates generally to apparatus and methods for testing a plurality of compositions in parallel, and more particularly, to apparatus and methods for testing compositions in contact with a porous medium.
Testing of chemical formulations often involves exposing the chemicals to a porous material such as a fabric which absorbs or interacts with the chemicals. Developers of fabric care products, for example, test different chemical compositions and formulations by exposing pieces of fabric to the compositions or formulations, and measuring the effects on the fabric's appearance, physical, or chemical properties which result. The types of chemicals or compositions tested in this way may include surfactants, polymers, dyes, bleaches, perfumes, buffers, electrolytes, builders (e.g., calcium sequestering agents), flame retarding agents, and others. Some of the benefits which may be desirable to deliver with such compositions, and which are therefore desirable to measure after exposing the fabric to the compositions or formulations, include release or removal of soils and stains, dye retention by a fabric during washing, prevention of dye transfer from one fabric to another, prevention of soil redeposition, resistance to the abrasion which occurs due to fabrics rubbing against each other during washing, building up of fibers to increase the life of a garment, reduction or prevention of wrinkles, reduction or prevention of static buildup, and improvement or preservation of the feel or texture of a fabric.
Currently used methods of testing for such benefits are extremely laborious, and limit the rate at which new compositions and formulations can be tested. The slowest testing methods involve washing fabrics in conventional full sized washing machines, or doing hand washing in a basin. Some degree of miniaturization has been introduced through the use of instruments such as the Washtec Linitester (manufactured by Roaches) or the Turgotometer (manufactured by Heraeus). In these instruments, washing is done in vessels of reduced volume, typically 0.5-2 liters, and multiple vessels are tested simultaneously. For example, the Heraeus Turgotometer consists of six one liter pots arranged in a straight line, each with an overhead stirrer to provide agitation similar to that found in top-loading washing machines. In the Roaches Washtec, up to twelve 1 liter vessels are mounted radially on a central axel, which is rotated to give an end-over-end tumbling motion and provide agitation. In both cases, the temperature is controlled through a thermostatted bath which surrounds the vessels.
Although these instruments represent a significant improvement over testing methods which utilize full scale washing apparatus, they still require a tremendous amount of manual labor, take up a great deal of space, and have limited throughput. Detergent formulations are extremely complex, often consisting of ten or more ingredients. While significant improvements in detergent performance can be and have been attained by introducing new ingredients or changing formulations, the size of the parameter space to be tested is enormous, including variables related to both chemical structure and formulations. It is therefore, desirable to develop methods and apparatus which allow high-throughput testing of compositions and formulations for fabric care. Ideally, it is desirable to obtain high throughput and miniaturization without sacrificing relevance of the results to more realistic conditions.
One possible method of high throughput testing of fabric care compositions and formulations is to place small, individual pieces of fabric in an array of small vessels, e.g. in a microtiter plate. One drawback to this method is that the individual pieces of fabric are difficult to handle and must be left in the wells during subsequent, handling, treatment, and analysis. If the pieces of fabric are removed from the wells, special handling equipment is required. Also, each piece of fabric may need to be individually labeled to prevent misidentification of the composition used to soak the fabric. Furthermore, it is difficult to simulate the agitation of fabric within a washing machine since the fabric is simply soaking in the fluid.
There is, therefore, a need for an apparatus and method for testing compositions in parallel with a continuous sheet of material having a plurality of porous test regions, which can be easily analyzed upon completion of testing. There is also a need for an apparatus and method for forcing fluid through the porous material or in contact with the material to simulate agitation of the porous material within the fluid.